Molecular sieve ssz-123, its synthesis and use

ABSTRACT

An aluminum-rich molecular sieve material of MFS framework type, designated SSZ-123, is provided. SSZ-123 can be synthesized using 1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium cations as a structure directing agent. SSZ-123 may be used in organic compound conversion and/or sorptive processes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Pat. ApplicationNo. 17/315,431, filed May 10, 2021, which claims priority to and thebenefit of U.S. Provisional Pat. Application No. 63/071,451, filed Aug.28, 2020, the disclosures of which are incorporated herein by referencein their entirety.

FIELD

This disclosure relates to a novel synthetic crystalline molecular sieveof MFS framework type, designated SSZ-123, its synthesis, and its use inorganic compound conversion and sorption processes.

BACKGROUND

Molecular sieves are a commercially important class of materials thathave distinct crystal structures with defined pore structures that areshown by distinct X-ray diffraction (XRD) patterns and have specificchemical compositions. The crystal structure defines cavities and poresthat are characteristic of the specific type of molecular sieve.

Molecular sieves are classified by the Structure Commission of theInternational Zeolite Association according to the rules of the IUPACCommission on Zeolite Nomenclature. According to this classification,framework-type zeolites and other crystalline microporous molecularsieves, for which a unique structure has been established, are assigneda unique three-letter code and are described, for example, in the “Atlasof Zeolite Framework Types” by Ch. Baerlocher, L.B. McCusker and D.H.Olson (Elsevier, Sixth Revised Edition, 2007).

ZSM-57 is a molecular sieve material having a unique two-dimensionalpore system consisting of intersecting 10-ring channels and 8-ringchannels. The framework structure of ZSM-57 has been assigned thethree-letter code MFS by the Structure Commission of the InternationalZeolite Association.

The composition and characterizing X-ray diffraction pattern of ZSM-57are disclosed in U.S. Pat. No. 4,873,067 which also describes theconventional synthesis of the molecular sieve in the presence of astructure directing agent comprising theN,N,N,N′,N′,N′-hexaethylpentanediammonium (HEPD) cation.

S-H. Lee et al. (J. Catal. 2000, 196, 158-166) report thatcrystallization of ZSM-57 in the presence of HEPD was possible only fromsynthesis mixtures within very narrow compositional ranges. Synthesismixtures with SiO₂/AI₂O₃ molar ratios less than 40 produced materialsother than ZSM-57.

According to the present disclosure, an aluminum-rich molecular sieve ofMFS framework type, designated SSZ-123, has now been synthesized using1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium cations as a structuredirecting agent.

SUMMARY

In a first aspect, there is provided a molecular sieve of MFS frameworktype having a molar ratio of SiO₂/Al₂O₃ in a range of from 10 to 35.

In a second aspect, there is provided an aluminosilicate molecular sieveof MFS framework type and, in its as-synthesized form, comprising1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium cations in its pores.

In a third aspect, there is provided a method of synthesizing amolecular sieve of MFS framework type, the method comprising (1)preparing a reaction mixture comprising: (a) a source of silicon; (b) asource of aluminum; (c) a source of an alkali or alkaline earth metal(M); (d) a structure directing agent comprising1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium cations (Q); (e) asource of hydroxide ions; and (f) water; and (2) subjecting the reactionmixture to crystallization conditions sufficient to form crystals of themolecular sieve.

In a fourth aspect, there is provided a process of converting afeedstock comprising an organic compound to a conversion product whichcomprises contacting the feedstock at organic compound conversionconditions with a catalyst comprising a molecular sieve of MFS frameworktype, wherein the molecular sieve has a molar ratio of SiO₂/Al₂O₃ in arange of from 10 to 35.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a Scanning Electron Micrograph (SEM) image of the productof Example 1.

FIG. 2 shows a powder X-ray diffraction (XRD) patterns of the product ofExample 1.

DETAILED DESCRIPTION Definitions

The term “framework type” as used herein has the meaning described inthe “Atlas of Zeolite Framework Types” by Ch. Baerlocher, L.B. McCuskerand D.H. Olson (Elsevier, Sixth Revised Edition, 2007).

The term “as-synthesized” is employed herein to refer to a molecularsieve in its form after crystallization, prior to removal of thestructure directing agent.

The term “anhydrous” is employed herein to refer to a molecular sievesubstantially devoid of both physically adsorbed and chemically adsorbedwater.

Synthesis of the Molecular Sieve

Molecular sieve SSZ-123 can be synthesized by: (1) preparing a reactionmixture comprising (a) a source of silicon; (b) a source of aluminum;(c) a source of an alkali or alkaline earth metal (M); (d) a structuredirecting agent comprising1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium cations; (e) a sourceof hydroxide ions; and (f) water; and (2) subjecting the reactionmixture to crystallization conditions sufficient to form crystals of themolecular sieve.

The reaction mixture can have a composition, in terms of molar ratios,within the ranges set forth in Table 1:

TABLE 1 Reactants Broadest Secondary SiO₂/Al₂O₃ 10 to 35 15 to 30 M/SiO₂0.05 to 0.50 0.10 to 0.50 Q/SiO₂ 0.01 to 0.30 0.05 to 0.20 OH/SiO₂ 0.10to 0.70 0.40 to 0.60 H₂O/SiO₂ 15 to 60 20 to 40

wherein M is an alkali or alkaline earth metal and Q comprises1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium cations.

Suitable sources of silicon include colloidal silica, precipitatedsilica, fumed silica, alkali metal silicates, and tetraalkylorthosilicates (e.g., tetraethyl orthosilicate).

Suitable sources of aluminum include hydrated alumina, aluminumhydroxide, alkali metal aluminates, aluminum alkoxides, andwater-soluble aluminum salts (e.g., aluminum nitrate).

The alkali or alkaline earth metal (M) is typically introduced into thereaction mixture in conjunction with the source of hydroxide ions.Examples of such metals include sodium and/or potassium, and alsolithium, rubidium, cesium, magnesium, and calcium. As used herein, thephrase “alkali or alkaline earth metal” does not mean the alkali metalsand alkaline earth metals are used in the alternative, but instead thatone or more alkali metals can be used alone or in combination with oneor more alkaline earth metals and that one or more alkaline earth metalscan be used alone or in combination with one or more alkali metals.

The structure directing agent used in preparing SSZ-123 comprises1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium cations (Q),represented by the following structure (1):

Suitable sources of Q are the hydroxides, chlorides, bromides, and/orother salts of the diquaternary ammonium compound.

The reaction mixture may contain seeds of a crystalline material, suchas an MFS framework type molecular sieve from a previous synthesis,desirably in an amount of from 0.01 to 10,000 ppm (e.g., 100 to 5000ppm) by weight of the reaction mixture. Seeding can be advantageous toimprove selectivity for SSZ-123 and/or to shorten the crystallizationprocess.

It is noted that the reaction mixture components can be supplied by morethan one source. Also, two or more reaction components can be providedby one source. The reaction mixture can be prepared either batchwise orcontinuously.

Crystallization and Post-Synthesis Treatment

Crystallization of the molecular sieve from the above reaction mixturecan be carried out under either static, tumbled or stirred conditions ina suitable reactor vessel, such as polypropylene jars or Teflon-lined orstainless-steel autoclaves, at a temperature of from 120° C. to 200° C.(e.g., 140° C. to 180° C.) for a time sufficient for crystallization tooccur at the temperature used (e.g., 1 day to 21 days, or 3 days to 14days). Crystallization is usually conducted in an autoclave so that thereaction mixture is subject to autogenous pressure.

Once the desired molecular sieve crystals have formed, the solid productis separated from the reaction mixture by standard separation techniquessuch as filtration or centrifugation. The recovered crystals arewater-washed and then dried, for several seconds to a few minutes (e.g.,from 5 seconds to 10 minutes for flash drying) or several hours (e.g.,from 4 to 24 hours for oven drying at 75° C. to 150° C.), to obtainas-synthesized SSZ-123 crystals having at least a portion of the organiccation within its pores. The drying step can be performed at atmosphericpressure or under vacuum.

The as-synthesized molecular sieve may be subjected to thermaltreatment, ozone treatment, or other treatment to remove part or all ofthe structure directing agent used in its synthesis. Removal of thestructure directing agent may be carried out by thermal treatment (i.e.,calcination) in which the as-synthesized molecular sieve is heated inair or inert gas at a temperature sufficient to remove part or all ofthe structure directing agent. While sub-atmospheric pressure may beused for the thermal treatment, atmospheric pressure is desired forreasons of convenience. The thermal treatment may be performed at atemperature at least 370° C. for at least a minute and generally notlonger than 20 hours (e.g., from 1 to 12 hours). The thermal treatmentcan be performed at a temperature of up to 925° C. For example, thethermal treatment may be conducted at a temperature of 400° C. to 600°C. in air for approximately 1 to 8 hours.

Any extra-framework metal cations in the molecular sieve can be replacedin accordance with techniques well known in the art (e.g., by ionexchange) with hydrogen, ammonium, or any desired metal cation.

Characterization of the Molecular Sieve

In its as-synthesized and anhydrous form, molecular sieve SSZ-123 canhave a chemical composition, in terms of molar ratios, within the rangesset forth in in Table 2:

TABLE 2 Broadest Secondary SiO₂/Al₂O₃ 10 to 35 15 to 30 Q/SiO₂ >0 to0.1 >0 to 0.1 M/SiO₂ >0 to 0.1 >0 to 0.1

wherein Q comprises 1-ethyl-1-[5-(triethylammonio)pentyl]piperidiniumcations and M is an alkali or alkaline earth metal.

In its calcined form, molecular sieve SSZ-123 can have a chemicalcomposition comprising the following molar relationship: Al₂O₃: (n)SiO₂wherein n is in a range of from 10 to 35 (e.g., 10 to 33, 10 to 30, 15to 35, 15 to 33, or 15 to 35).

Powder XRD patterns representative of MFS framework type molecularsieves can be referenced in the “Collection of Simulated XRD PowderPatterns for Zeolites” by M.M.J. Treacy and J.B. Higgins (Elsevier,Fifth Revised Edition, 2007).

The powder XRD patterns presented herein were collected by standardtechniques. Minor variations in the diffraction pattern can result fromvariations in the mole ratios of the framework species of the particularsample due to changes in lattice constants. In addition, sufficientlysmall crystals will affect the shape and intensity of peaks, leading tosignificant peak broadening. Minor variations in the diffraction patterncan also result from variations in the organic compound used in thepreparation. Calcination can also cause minor shifts in the XRD pattern.Notwithstanding these minor perturbations, the basic crystal latticestructure remains unchanged.

Industrial Applicability

Molecular sieve SSZ-123 (where part or all of the structure directingagent is removed) may be used as a sorbent or as a catalyst to catalyzea wide variety of organic compound conversion processes including manyof present commercial/industrial importance. Examples of chemicalconversion processes which are effectively catalyzed by SSZ-123, byitself or in combination with one or more other catalytically activesubstances including other crystalline catalysts, include thoserequiring a catalyst with acid activity. Examples of organic conversionprocesses which may be catalyzed by SSZ-123 include cracking,hydrocracking, disproportionation, alkylation, oligomerization, andisomerization.

As in the case of many catalysts, it may be desirable to incorporateSSZ-123 with another material resistant to the temperatures and otherconditions employed in organic conversion processes. Such materialsinclude active and inactive materials and synthetic or naturallyoccurring zeolites as well as inorganic materials such as clays, silicaand/or metal oxides such as alumina. The latter may be either naturallyoccurring, or in the form of gelatinous precipitates or gels, includingmixtures of silica and metal oxides. Use of a material in conjunctionwith SSZ-123 (i.e., combined therewith or present during synthesis ofthe new material) which is active, tends to change the conversion and/orselectivity of the catalyst in certain organic conversion processes.Inactive materials suitably serve as diluents to control the amount ofconversion in a given process so that products can be obtained in aneconomic and orderly manner without employing other means forcontrolling the rate of reaction. These materials may be incorporatedinto naturally occurring clays (e.g., bentonite and kaolin) to improvethe crush strength of the catalyst under commercial operatingconditions. These materials (i.e., clays, oxides, etc.) function asbinders for the catalyst. It is desirable to provide a catalyst havinggood crush strength because in commercial use it is desirable to preventthe catalyst from breaking down into powder-like materials. These clayand/or oxide binders have been employed normally only for the purpose ofimproving the crush strength of the catalyst.

Naturally occurring clays which can be composited with SSZ-123 includethe montmorillonite and kaolin family, which families include thesub-bentonites, and the kaolins commonly known as Dixie, McNamee,Georgia and Florida clays or others in which the main mineralconstituent is halloysite, kaolinite, dickite, nacrite, or anauxite.Such clays can be used in the raw state as originally mined or initiallysubjected to calcination, acid treatment or chemical modification.Binders useful for compositing with SSZ-123 also include inorganicoxides, such as silica, zirconia, titania, magnesia, beryllia, alumina,and mixtures thereof.

In addition to the foregoing materials, SSZ-123 can be composited with aporous matrix material such as silica-alumina, silica-magnesia,silica-zirconia, silica-thoria, silica-beryllia, silica-titania as wellas ternary compositions such as silica-alumina-thoria,silica-alumina-zirconia silica-alumina-magnesia andsilica-magnesia-zirconia.

The relative proportions of SSZ-123 and inorganic oxide matrix may varywidely, with the SSZ-123 content ranging from 1 to 90 wt.% (e.g., 2 to80 wt.%) of the composite.

EXAMPLES

The following illustrative examples are intended to be non-limiting.

Example 1

2.45 g of deionized water, 0.37 g of 45% KOH solution, 2.68 g of 17.8%1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium hydroxide solution,0.08 g of 50% Reheis F-2000 aluminum hydroxide dried gel and 2.00 g ofLUDOX® AS-30 colloidal silica (30 wt.% suspension in water) were mixedtogether in a Teflon liner. The resulting gel was stirred until itbecame homogeneous. The liner was then capped and placed within a ParrSteel autoclave reactor. The autoclave was then put in an oven heated at160° C. for 12 days with tumbling at 43 rpm. The solid products wererecovered from the cooled reactor by centrifugation, washed withdeionized water and dried at 95° C.

The resulting product was analyzed by SEM and powder XRD. A SEM image isshown in FIG. 1 and indicates a uniform field of crystals. The powderXRD pattern of the as-synthesized material is shown in FIG. 2 and isconsistent with the material having the MFS framework type structure.

The product had a SiO₂/Al₂O₃ molar ratio of 18.8, as determined byInductively Coupled Plasma - Atomic Emission Spectroscopy (ICP-AES)elemental analysis.

Example 2

1.84 g of deionized water, 0.28 g of a 45% KOH solution, 2.01 g of a17.8% 1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium hydroxidesolution, 0.05 g of Reheis F-2000 aluminum hydroxide dried gel and 1.50g of LUDOX® AS-30 colloidal silica were mixed together in a Teflonliner. The gel was stirred until it became homogeneous. The liner wasthen capped and placed within a Parr Steel autoclave reactor. Theautoclave was then put in an oven heated at 160° C. for 10 days withtumbling at 43 rpm. The solid products were recovered from the cooledreactor by centrifugation, washed with deionized water and dried at 95°C.

Analysis by powder XRD showed the product to be an MFS framework typemolecular sieve.

The product had a SiO₂/Al₂O₃ molar ratio of 21.7, as determined byICP-AES elemental analysis.

Example 3

2.46 g of deionized water, 0.37 g of a 45% KOH solution, 2.68 g of a17.8% 1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium hydroxidesolution, 0.05 g of Reheis F-2000 aluminum hydroxide dried gel and 2.00g of LUDOX® AS-30 colloidal silica were mixed together in a Teflonliner. The gel was stirred until it became homogeneous. The liner wasthen capped and placed within a Parr Steel autoclave reactor. Theautoclave was then put in an oven heated at 160° C. for 10 days withtumbling at 43 rpm. The solid products were recovered from the cooledreactor by centrifugation, washed with deionized water and dried at 95°C.

Analysis by powder XRD showed the product to be an MFS framework typemolecular sieve.

The product had a SiO₂/Al₂O₃ molar ratio of 31.2, as determined byICP-AES elemental analysis.

Example 4

3.20 g of deionized water, 0.37 g of a 45% KOH solution, 1.79 g of a17.8% 1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium hydroxidesolution, 0.04 g of Reheis F-2000 aluminum hydroxide dried gel and 2.00g of LUDOX® AS-30 colloidal silica were mixed together in a Teflonliner. The gel was stirred until it became homogeneous. The liner wasthen capped and placed within a Parr Steel autoclave reactor. Theautoclave was then put in an oven heated at 160° C. for 10 days withtumbling at 43 rpm. The solid products were recovered from the cooledreactor by centrifugation, washed with deionized water and dried at 95°C.

Analysis by powder XRD showed the product to be a mixture of an MFS-typemolecular sieve and a dense phase.

Example 5

2.44 g of deionized water, 0.37 g of a 45% KOH solution, 2.68 g of a17.8% 1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium hydroxidesolution, 0.10 g of Reheis F-2000 aluminum hydroxide dried gel and 2.00g of LUDOX® AS-30 colloidal silica were mixed together in a Teflonliner. The resulting gel was stirred until it became homogeneous. Theliner was then capped and placed within a Parr Steel autoclave reactor.The autoclave was then put in an oven heated at 160° C. for 10 days withtumbling at 43 rpm. The solid products were recovered from the cooledreactor by centrifugation, washed with deionized water and dried at 95°C.

Analysis by powder XRD showed the product to be a mixture of an MFSframework type molecular sieve and an unknown phase.

Example 6

Example 5 was repeated except that 5 wt.% of as-synthesized MFS seedcrystals prepared from Example 1 were added to the reaction mixture andthe reaction time was reduced to 7 days.

Analysis by powder XRD showed the product to be a pure phase MFSframework type molecular sieve.

The product had a SiO₂/Al₂O₃ molar ratio of 16.5, as determined byICP-AES elemental analysis.

Example 7

The as-synthesized molecular sieve product from Example 1 was calcinedinside a muffle furnace under a flow of air at a temperature of about540° C. for about 5 hours. After cooling, the sample was analyzed bypowder XRD. Powder XRD indicated that the material remains stable aftercalcination to remove the structure directing agent.

Example 8

The calcined material from Example 7 was treated with 10 mL (per g ofmolecular sieve) of a 1 N ammonium nitrate solution at 95° C. for 2hours. The solution was cooled, decanted off and the same processrepeated. The product (NH₄-SSZ-123) after drying was subjected to amicropore volume analysis using N₂ as adsorbate and via the BET method.The molecular sieve exhibited a micropore volume of 0.14 cm³/g.

1. A molecular sieve of MFS framework type having a molar ratio ofSiO₂/Al₂O₃ in a range of 10 to
 35. 2. The molecular sieve of claim 1,wherein the molar ratio of SiO₂/Al₂O₃ is in a range of 15 to
 30. 3. Themolecular sieve of claim 1, further comprising1-ethyl-1-[5-(triethylammonio)pentyl]piperidinium cations in its pores.